In an electrical communication system, it is sometimes advantageous to transmit data in the form of differential signals over a pair of conductive paths (i.e., a conductive path pair) rather than a single conductive path, where the transmitted signal comprises the voltage difference between the conductive paths without regard to the absolute voltages present. Each conductive path in a conductive path pair is capable of picking up electrical noise from outside sources, e.g., neighboring data lines, or other sources. Differential signals may be advantageous to use due to the fact that the signals are less susceptible to these outside sources.
A concern with differential signals is electrical noise that is caused by neighboring differential conductive path pairs, where the individual conductors on each conductive path pair couple (inductively or capacitively) in an unequal manner that results in added noise to the neighboring conductive path pair. This is referred to as crosstalk.
The ability of a data connector to support higher bandwidths depends, at least in part, on the amount of crosstalk that it adds to the system. Ideally, the connector should be transparent to the system, meaning it should not add any crosstalk to the system. For systems using RJ45 style connectors, as are known in the art, crosstalk is inherent to the conductor pair layout. For this type of connector, crosstalk reduction and suppression become critical. Some of the crosstalk reduction efforts focus on isolation, minimizing capacitive and inductive imbalances, and reducing the overall path length of conductors within the connector.
FIGS. 1-3 provide an overview of a known RJ45 style connector. FIG. 1 depicts a connector 2 shown comprising a known communication jack 4 and a communication plug 6 in a connected position, although both communication jack 4 and communication plug 6 can separately each be considered a connector. FIG. 2 depicts the known communication jack 4, which is shown comprising plug interface contacts (PICs) 10, and FIG. 3 depicts the communication plug 6, which is shown comprising plug contacts 12.
RJ45 connector parameters are defined by the ANSI/TIA-5531-C.2 standard, and noise suppression typically takes place inside the communication jack 4 of the connector 2. The effectiveness of the suppression depends in part on (i) the distance from the plug contacts 12 on the communication plug 6 and the PICs 10 on the communication jack 4 to the compensation elements in the communication jack 4, and (ii) inductive and capacitive balance.
For interoperability and long term reliability, the communication jack 4 is also required to meet stringent physical and mechanical requirements, such as certain contact angles, normal force, and insertion cycles relative to the PICs 10 on the communication jack 4. Crosstalk suppression favors a shorter contact length, yet the mechanical requirements often require longer contacts than can be readily used for crosstalk suppression. In most cases, the length required to meet the mechanical requirements is a limiting factor. Hence, it becomes beneficial for higher bandwidth connectors to have PICs that meet mechanical requirements while remaining short enough to enable effective crosstalk suppression.
An exploded perspective illustration of one type of communication jack 4 is depicted in FIG. 4. The communication jack 4 is shown comprising a housing 14 that fits an RJ45 communication plug, a nose 16, a rigid printed circuit board (PCB) 18 connected to insulation displacement contacts (IDCs) 20, a rear sled 22 that holds the IDCs 20, and a wire cap 24 that assists wires within cabling to connect to the IDCs 20. The nose 16 may sit within the housing 14 and provides an interface between the plug contacts and the rigid PCB 18. In this respect, as shown, the nose 16 comprises eight PICs 28 that each mate with a respective plug contact on the communication plug (not shown) on a contact surface and with a through hole on the rigid PCB 18 at an end. As shown, the PICs 28 wrap around a mandrel 34 on the nose 16. The PICs 28 may be supported in the nose 16 by a front bottom sled 30 and a front top sled 32, each mechanically coupled to the PICs 28.
The nose 16 may also include a flexible PCB 26 that provides crosstalk compensation when the flexible PCB 26 is in contact with the PICs 28. As shown, the flexible PCB 26 wraps around the same mandrel 34 as the PICs 28, and includes conductive traces on at least one side and/or layer that facilitate electrical contact with the PICs 28.
The interaction of the communication jack 4 and communication plug 6 may be seen in FIG. 5. In the communication jack 4, the PICs 28 operate dually as electrical contacts and mechanical springs. However, as discussed above, the electrical and mechanical functions of the PICs 28 are somewhat opposed. The PICs 28 are designed to maintain a contact normal force of about 100 grams on the plug contacts 12 in the communication plug in the window of movement. However, the mechanical length necessary to achieve this contact normal force may be detrimental to electrical performance due to inductive and capacitive coupling between a given PIC 28 and other PICs 28, as increased PIC length results in increased coupling.
FIG. 5 shows a first contact point 38, marking the contact between the individual plug contacts 12 and the PICs 28, and a second contact point 40, marking the contact between the PICs 28 and the flexible PCB 26. The distance 36 between the first contact point 38 and the second contact point 40 is smaller than on a typical communication jack that does not utilize a flexible PCB 26. The shorter distance 36 increases the effectiveness of crosstalk compensation in the flexible PCB 26.
However, while the communication jack of FIGS. 1-5 provides some improvement in crosstalk suppression, the design also is subject to potential difficulties. First, the flexible PCB 26 costs more than the standard rigid PCB 18. Additionally, due to the small size and low weight of the flexible PCB 26 there can be difficulties in handling during manufacturing.
Thus, manufacture of the circuit board components for communication jack 4 requires two different manufacturing processes for the flexible PCB 26 and the rigid PCB 18. In some cases, these processes can have etching tolerances at opposite ends of the tolerance spectrum. Such mismatch along the tolerance spectrum results in a mismatch in the balancing capacitors located on the flexible PCB 26 and the rigid PCB 18. The unbalanced capacitors will fail to cancel the crosstalk effectively and will yield a connector with poor performance. The limitations and complexity of the manufacture of the communication jack 4 may additionally require that the section of the PICs 28 from the sled mandrel 34 to the rigid PCB 18 be routed in a particular way that may add to coupling within the connector as well as between adjacent connectors. In order to reduce coupled crosstalk between the connectors, spacing must be increased between the connectors, or foil wrap must be added around the connector. The increased spacing reduces the number of connectors in a given space and addition of the foil increases the connector cost.